J. Zrzavy et al., Myzostomida are not annelids: Molecular and morphological support for a clade of animals with anterior sperm flagella, CLADISTICS, 17(2), 2001, pp. 170-198
Citations number
146
Categorie Soggetti
Biology
Journal title
CLADISTICS-THE INTERNATIONAL JOURNAL OF THE WILLI HENNIG SOCIETY
The myzostomes are animals with five pairs of parapodia, living as commensa
ls or (endo)parasites mostly on crinoid and ophiuroid echinoderms. They are
generally considered aberrant annelids, possibly phyllodocidan polychaetes
. A phylogenetic analysis of 18S and 28S ribosomal DNA sequence data of Myz
ostoma glabrum, together with 60 morphological, developmental, ultrastructu
ral, and life-history characters, is presented to show that myzostomes are
a sister group of the Cycliophora, closely related to the rotifer-acanthoce
phalan clade (= Syndermata). Myzostomes and syndermates share predominantly
the highly derived spermatozoa with anteriorly directed flagella (cyclioph
oran sperm is insufficiently known). The myzostome-cycliophoran-syndermate
clade, accommodated within the Platyzoa (including Platyhelminthes s. str.,
Gastrotricha, Gnathostomulida, Syndermata, Cycliophora, and Myzostomida),
is strongly supported by most analyses, regardless of alignment parameters,
character combinations and weighting, species sampling, and tree-building
methods. The new name Prosomastigozoa ("forward-flagellar animals") is prop
osed for the group including three phyla (Cycliophora, Myzostomida, and Syn
dermata). (C) 2001 the Willi Hennig Society.